Blocked isocyanates

Abstract

A blocked polyisocyanate of the formula R-Y.sub.m where R is an m valent aliphatic, cycloaliphatic, heterocyclic or aromatic residue; each Y, which may be the same or different, is ##STR1## where R 1 is, or, when n is more than 1, each R 1 , which may be the same or different, is an alkyl, alkenyl, aralkyl, N-substituted carbamyl, phenyl, NO 2 , halogen or ##STR2## group where R 2 is a C 1 -C 4 alkyl group; n is 0, 1, 2 or 3; and m is an integer greater than 1 is useful in paint compositions.

We claim: 
     
       1. In a storage-stable coating composition comprising an active hydrogen-containing compound and a blocked polyisocyanate of the formula:   R-Y.sub.m     wherein R is an m valent aliphatic, cycloaliphatic, heterocyclic or aromatic residue, m is an integer greater than 1 and Y is a blocking group, the improvement whereby said composition is curable by heat unblocking at 100° C. to 120° C., and each Y, which may be the same or different, is ##STR7## wherein R 1  is, or, where n is more than 1, each R 1 , which may be the same or different, is a C 1  -C 4  alkyl, C 1  -C 4  alkenyl, phenyl C 1  -C 4  alkyl, phenyl, NO 2 ,<halogen or ##STR8## group where R 2  is a C 1  -C 4  alkyl group; and n is 0, 1, 2 or 3, provided that, when R is an aromatic residue the groups Y are not directly attached to an aromatic nucleus.   
     
     
       2. A composition according to claim 1 wherein, in said blocked polyisocyanate, at least one Y is ##STR9## 
     
     
       3. A composition according to claim 2 wherein in at least one Y is ##STR10## 
     
     
       4. A composition according to claim 1 wherein, in said blocked polyisocyanate, m is from 2 to 6. 
     
     
       5. A composition according to claim 1 wherein, in said blocked polyisocyanate, R is a hydrocarbon group optionally substituted by an alkoxy group. 
     
     
       6. A composition according to claim 1 wherein, in said blocked polyisocyanate, R is a divalent radical derived from isophorone of formula ##STR11## 
     
     
       7. A composition according to claim 1 wherein said blocked polyisocyanate has a biuret structure or an allophanate group. 
     
     
       8. A composition according to claim 1 wherein said active hydrogen-containing compound is an amine or an alcohol. 
     
     
       9. A composition according to claim 8 wherein said active hydrogen-containing compound is 1,4-butanediol. 
     
     
       10. A composition according to claim 1 further comprising a catalyst. 
     
     
       11. A composition according to claim 10 wherein said catalyst is dibutyl tin dilaurate or tri-ethylene diamine. 
     
     
       12. A composition according to claim 1 wherein said active hydrogen-containing compound is a pigment carrier containing active hydrogen groups, said composition further comprising a pigment. 
     
     
       13. A composition according to claim 12 having 0.5 to 2 blocked isocyanate groups per active hydrogen-containing group. 
     
     
       14. A composition according to claim 1 wherein, in said polyisocyanate, R is an aliphatic group. 
     
     
       15. A composition according to claim 1 wherein, in said polyisocyanate, R is an cycloaliphatic group. 
     
     
       16. A composition according to claim 1, wherein said polyisocyanate is a di-isocyanate.